TWI765728B - Polyester release film and method for preparing the same - Google Patents

Abstract

The present disclosure relates to a polyester release film and a method for preparing the same. According to the present disclosure, a polyester release film made of a non-silicone-based material and having excellent peelability and low triboelectricity, and a method for preparing the same, are provided. The polyester release film may be suitably used as a base film for release in the preparation of a thin polarizing plate.

Description

Polyester release film and preparation method thereof

The present disclosure relates to a polyester release film and a preparation method thereof.

With the trend of enlargement and thinning of display units in image display devices, the demand for thinning polarizing plates is gradually increasing.

One method for reducing the thickness of the polarizing plate is to thin a typical polarizer protective material such as polyethylene terephthalate (PET) or triacetyl cellulose (TAC). Another method for reducing the thickness of the polarizing plate is to replace the polarizer protective material with a coating having barrier properties (hereinafter referred to as "barrier coating").

To form the barrier coating, the composition for forming the barrier coating is uniformly coated on any base layer, cured, and then peeled off.

To obtain a good quality barrier coating, the cured barrier coating should be sufficiently delaminated from the base layer.

However, when a polysiloxane release film with low surface energy is used as a base layer, it is difficult to form a barrier coating with a uniform thickness, and static electricity problems may occur due to polysiloxane.

In the present disclosure, a polyester release film with excellent peelability and low triboelectricity is provided.

In addition, a method for preparing the above polyester release film is provided.

According to an embodiment of the present disclosure, a polyester release film is provided, the polyester release film includes a polyester base layer and a release layer formed on at least one surface of the base layer, wherein the release layer includes a Adhesives for polyester resins and polyolefin waxes dispersed on the adhesives, having 3.94 gf/cm (i.e. 10 gf/in) or less than 3.94 gf/cm (i.e. 10 gf/in) Peel strength and triboelectricity less than 500 volts.

According to another embodiment of the present disclosure, there is provided a polyester release film for a thin polarizing plate, the polyester release film includes a polyester base layer with a thickness of 20 nm to 200 nm, A release layer with a thickness of 20 nanometers to 200 nanometers is formed by series coating on the base layer, wherein the release layer comprises an adhesive containing polyester resin and a polyolefin wax dispersed on the adhesive, and has a thickness of 3.94 grams Force/cm (ie 10 gf/inch) or peel strength less than 3.94 gf/cm (ie 10 gf/inch) and triboelectricity less than 500 volts.

According to another embodiment of the present disclosure, there is provided a method for preparing a polyester release film, the method comprising the steps of: (i) preparing a polyester stretched in a machine direction (MD) base layer; (ii) forming a release layer by coating at least one surface of the polyester base layer with an aqueous coating composition comprising a polyester resin-containing binder and a dispersion a polyolefin wax on the adhesive; and (iii) a heat-treated laminate comprising a polyester base layer and a release layer formed on the polyester base layer, while in the transverse direction (TD; TD) ) up-stretching the laminate, wherein step (iii) is performed while passing the laminate through a heat treatment device in which the total heat of air supplied to the passing area is 222,000 kcal/min to 229,000 kcal/ minute.

Hereinafter, polyester release films and methods for preparing the same according to embodiments of the present invention will be described in more detail.

The terms are used to refer to specific embodiments only, and are not intended to limit the present disclosure unless explicitly stated.

Singular expressions in the present disclosure may include paraphrased expressions unless they are expressed differently in context.

The terms "comprising", "including" and the like in this disclosure are used to designate certain features, regions, integers, steps, operations, elements and/or components, and these do not exclude other specific features, regions, integers , steps, operations, the presence or addition of elements and/or components.

I. Polyester release film

According to an embodiment of the present disclosure, a polyester release film is provided, the polyester release film includes a polyester base layer and a release layer formed on at least one surface of the base layer, The release layer comprises an adhesive containing polyester resin and a polyolefin wax dispersed on the adhesive, and Have a peel strength of 3.94 gf/cm (ie 10 gf/inch) or less than 3.94 gf/cm (ie 10 gf/inch) and a triboelectricity of less than 500 volts.

According to the continuous research of the present inventors, it has been confirmed that when an aqueous coating composition containing a polyester resin and a polyolefin wax is coated on a uniaxially stretched base layer by a tandem coating method, the thin polarizing plate can be When the release layer is formed in the base film for release used in the preparation of the polyester film, a polyester release film with excellent coating processability and peel strength can be provided.

The polyester release film can exhibit excellent releasability in the post-processing using it (such as the process of forming a barrier coating on the release film, etc.), and can have low triboelectricity, thereby preventing static electricity caused by pollution.

The polyester release film includes a polyester base layer and a release layer formed on at least one surface of the base layer.

The polyester base layer is made of polyester resin. As the polyester base layer, a known polyester base layer in the field to which the present invention pertains can be used without particular limitation. For example, the polyester base layer may be made of polyethylene terephthalate, polyethylene naphthalate, or the like. As a non-limiting example, in terms of achieving weather resistance and hydrolysis resistance, the base layer may be formed of a polymer having an intrinsic viscosity of 0.6 deciliter/gram to 0.8 deciliter/gram Made of ethylene phthalate.

The release layer is formed on one surface or both surfaces of the polyester base layer. Preferably, the release layer is formed on one surface of the polyester base layer.

The release layer includes an adhesive containing polyester resin and a polyolefin wax dispersed on the adhesive.

The polyester resin contained in the binder is a resin obtained by condensation polymerization of an acid component containing a dicarboxylic acid as a main component and a diol component containing an alkylene glycol as a main component. As the acid component, terephthalic acid or its alkyl ester or phenyl ester can be mainly used, and a part thereof can be treated with isophthalic acid, oxyethoxybenzoic acid, adipic acid, sebacic acid, 5-sulfonic acid Substituted with sodium isophthalate, sulfoterephthalic acid, etc. As the diol component, ethylene glycol or diethylene glycol can be mainly used, and a part of it can be mixed with propylene glycol, 1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1 , 4-dioxyethoxybenzene, bisphenol, polyoxyethylene glycol, etc.

As a non-limiting example, a polyester resin may be polymerized by polycondensation of 50 mol % of a diol component containing diethylene glycol and ethylene glycol in a molar ratio of 5:5 with 50 mol % of a diol component containing mol % Obtained from the acid components of terephthalic acid and sulfoterephthalic acid in a ratio of 8.5:1.5.

When the weight average molecular weight of the polyester resin is 2000 g/mol to 25,000 g/mol, it may be advantageous for the release layer to have suitable solvent resistance. Preferably, the weight average molecular weight of the polyester resin may be 2000 g/mol to 25,000 g/mol, 2000 g/mol to 20,000 g/mol, 3000 g/mol to 20,000 g/mol or 3000 g/mol. g/mol to 15,000 g/mol.

In the present disclosure, the weight average molecular weight means the weight average molecular weight converted with polystyrene measured by GPC. Polyphenylene used in the measurement by GPC In the process of converting the weight average molecular weight of ethylene, commonly known analytical equipment, detectors such as refractive index detectors and columns for analysis can be used, and generally applied temperature conditions, solvents and flow rates can be applied .

As a specific example of the measurement conditions, a polymer resin such as a polyurethane resin is dissolved in tetrahydrofuran ( tetrahydrofuran; THF)) and then filtered using a 0.45 micron pore size syringe filter, followed by injection into 20 microliters of GPC. The mobile phase for GPC was tetrahydrofuran (THF) and flowed at a flow rate of 1.0 mL/min. An Agilent PLgel 5 micron Guard (7.5 x 50 mm) and two Agilent PLgel 5 micron Mixed D (7.5 x 300 mm) columns were used in series, and an Agilent 1260 Infinity II system, RI detector was used in the Measured at 40°C.

Polystyrene standards (Standards A, B, C, D) obtained by dissolving polystyrene with various molecular weights in tetrahydrofuran at a concentration of 0.1 (w/w) % were passed through a 0.45 micron pore size syringe Filter filtered and then injected into GPC to obtain the weight average molecular weight (Mw) of the polymer using the calibration curve formed therefrom.

Standard A (Mp): 791,000/27,810/945

Standard B (Mp): 282,000/10,700/580

Standard C(Mp): 126,000/4430/370

Standard D (Mp): 51,200/1920/162

The release layer may further contain acrylic resin as an adhesive.

For example, the binder may contain polyester resin and acrylic resin in a weight ratio of 1:0.5 to 1:1.5 and preferably 1:1 based on solids content.

Preferably, the acrylic resin may contain a radically polymerizable unsaturated monomer having a glycidyl group as a comonomer in an amount of 20 mol % to 80 mol % of the entire monomer component. The free-radically polymerizable unsaturated monomer having a glycidyl group improves the strength of the release layer through a cross-linking reaction, and prevents leakage of low polymers. The free-radically polymerizable unsaturated monomer having a glycidyl group may include glycidyl acrylate, glycidyl methacrylate, aryl glycidyl ether, and the like.

Examples of the radically polymerizable unsaturated monomer copolymerized with the radically polymerizable unsaturated monomer having a glycidyl group may include vinyl esters, unsaturated carboxylates, unsaturated carboxylamides, unsaturated nitriles, Unsaturated carboxylic acids, allyl compounds, nitrogen-containing vinyl monomers, hydrocarbon vinyl monomers, and vinyl silane compounds. As the vinyl ester, vinyl propionate, vinyl stearate, vinyl chloride and the like can be used.

As the unsaturated carboxylic acid ester, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, butyl maleate, cis Octyl butenedioate, butyl fumarate, octyl fumarate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate and the like. As the unsaturated carboxylic acid amide, acrylamide, methacrylamide, methylol acrylamide, butoxymethylol acrylamide, and the like can be used. As the unsaturated nitrile, acrylonitrile and the like can be used.

As the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid ester, fumaric acid ester, itonic acid ester and the like can be used By. As the allyl compound, allyl acetate, allyl methacrylate, allyl acrylate, allyl iconic acid, diallyl iconic acid, and the like can be used. As the nitrogen-containing vinyl monomer, vinylpyridine, vinylimidazole, and the like can be used.

As the hydrocarbon vinyl monomer, ethylene, propylene, hexene, octene, styrene, vinyltoluene, butadiene, and the like can be used. As the vinylsilane compound, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, γ- Methacrylooxypropyltrimethoxysilane, gamma-methacrylooxypropyldimethoxysilane and the like.

As a non-limiting example, the acrylic resin may be a copolymer of 40-60 mol% glycidyl acrylate and 40-60 mol% propionic acid.

The acrylic resin may preferably have a weight average molecular weight of 20,000 g/mol to 70,000 g/mol. More preferably, the weight average molecular weight of the polyester resin may be 20,000 g/mol to 60,000 g/mol, 30,000 g/mol to 60,000 g/mol, 40,000 g/mol to 60,000 g/mol or 45,000. g/mol to 55,000 g/mol.

The release layer contains polyolefin wax dispersed on the adhesive.

The specific kind of polyolefin wax is not particularly limited, but at least one selected from the group consisting of polyethylene wax and polypropylene wax can be preferably used.

The polyolefin wax may be contained in an amount of 10 to 40 parts by weight based on 100 parts by weight of the adhesive. In order to make the release layer exhibit suitable peel strength, it is preferable to contain polyolefin wax in an amount of 10 parts by weight or more based on 100 parts by weight of the adhesive. However, if the polyolefin wax is added to the release layer in excess, it may cause reverse transfer problems and a reduction in process coatability. Therefore, the polyolefin wax is preferably contained in an amount of 40 parts by weight based on 100 parts by weight of the adhesive.

For example, based on 100 parts by weight of the adhesive, it can contain 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more 20 parts by weight or 25 parts by weight or more, and polyolefin wax in an amount of 40 parts by weight or less, 35 parts by weight or less, or 30 parts by weight or less. Specifically, based on 100 parts by weight of the adhesive, it can contain 10 parts by weight to 40 parts by weight, 15 parts by weight to 40 parts by weight, 15 parts by weight to 35 parts by weight, 20 parts by weight to 35 parts by weight, and 20 parts by weight Polyolefin wax in an amount of from 30 parts by weight to 25 parts by weight to 30 parts by weight.

The thicknesses of the base layer and the release layer are not particularly limited, and can be adjusted according to the specific field of application of the polyester release film. For example, the thickness of the base layer may be 10 to 100 micrometers, and the thickness of the release layer may be 20 to 200 nanometers.

In the polyester release film, the base layer may be biaxially stretched in the machine direction (MD) and the transverse direction (TD), and the release layer may be uniaxially stretched in the transverse direction (TD).

The polyester release film can have excellent peelability and low triboelectricity because it satisfies the properties described above.

For example, the polyester release film can have 3.94 gf/cm (ie 10 gf/in) or less than 3.94 gf/cm (ie 10 gf/in), 0.787 gf/cm (ie 2 gf/cm) gf/in) to 3.94 gf/cm (i.e. 10 gf/in), 1.97 gf/cm (i.e. 5 gf/in) to 3.94 gf/cm (i.e. 10 gf/in) ) or an excellent peel strength of 3.94 gf/cm (i.e. 5 gf/in) to 3.15 gf/cm (i.e. 8 gf/in).

In the present disclosure, peel strength can be measured according to the standard test method of ASTM D903. Specifically, the peel strength can be measured by including the following steps: preparing a first sample in which a cured UV resin layer having a thickness of 10 microns is formed on the release layer of the polyester release film; by using 2 Kilo rubber rollers will TESA tape in the first A second sample was prepared by rubbing back and forth twice on the cured UV resin layer of the product, and then cutting it to a size of 2.5 mm x 15 cm; and applying a load of 70 g/cm 2 to the second sample and After standing at room temperature for 30 minutes, the TESA tape was peeled off at 180° at a peel rate of 300 mm/min using a peel tester.

Also, the lower triboelectricity of the polyester release film may be less than 500 volts, 150 volts to 450 volts, 200 volts to 450 volts, 200 volts to 400 volts, 250 volts to 400 volts, or 250 volts to 350 volts.

In the present disclosure, triboelectricity is measured according to the standard test method of KS K 0555. Specifically, the triboelectricity can be obtained by measuring the static electricity of the polyester release film by using a conventional rotating electrostatic tester. At this time, by rubbing the A side (the side with the release layer in the polyester release film) and the B side (the side where the release layer was not formed in the polyester base layer sample) at 300 revolutions/180 seconds amount of static electricity.

In addition, polyester release films can exhibit excellent process coatability while having lower haze.

For example, the haze of the polyester release film may be 3.90% or less. Preferably, the haze of the polyester release film may be 3.90% or less, 3.50% to 3.90%, 3.60% to 3.90%, 3.60% to 3.85%, 3.70% to 3.85%, or 3.75% to 3.85% .

In addition, the excellent process coatability of the polyester release film can satisfy the following Equation 1: [Equation 1] N _H =0

In Equation 1, _NH is the number of pores per unit area (square meter) generated when UV resin is coated to a thickness of 10 microns on the release layer of the polyester release film and the UV resin is cured .

That is, in any preparation process using the polyester release film as the base layer, when any resin layer is formed on the release layer, substantially no small holes are formed on the release layer, thereby showing excellent performance. Process coatability.

And, the polyester release film may have a total light transmittance of 90% to 95%, a water contact angle of 85 to 90 degrees, a diiodomethane contact angle of 50 to 60 degrees, and 30 mN/m to 35 Surface energy in millinewtons/meter.

According to another embodiment of the present disclosure, there is provided a polyester release film for a thin polarizing plate, the polyester release film includes a polyester base layer with a thickness of 20 nm to 200 nm, A release layer with a thickness of 20 nanometers to 200 nanometers is formed by series coating on the base layer, wherein the release layer comprises an adhesive containing polyester resin and a polyolefin wax dispersed on the adhesive, and has a thickness of 3.94 grams Force/cm (ie 10 gf/inch) or peel strength less than 3.94 gf/cm (ie 10 gf/inch) and triboelectricity less than 500 volts.

In the polyester release film, the specific details of the polyester base layer and the release layer are the same as the polyester base layer and the release layer described above.

In the polyester release film, in particular, the release layer is formed by tandem coating on the polyester base layer. The release layer can be formed by coating an aqueous coating composition containing a binder and a polyolefin wax on the polyester base layer using a tandem coating method.

Since the release layer is formed by the tandem coating method, it has excellent adhesion to the polyester base layer, and can exhibit excellent moisture resistance and solvent resistance, while having a thin coating thickness.

Since the polyester release film has excellent releasability and low triboelectricity, it can be suitably used as a release base film in the production of thin polarizing plates.

By way of non-limiting example, when preparing thin polarizing plates, barrier coatings, polyvinyl alcohol resin layers, adhesive layers, and materials such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), or polymethyl methacrylate The resin layer of polymethyl methacrylate (PMMA) can be sequentially laminated on the base layer of the polyester release film to form a laminate. Also, the polyester release film can be removed from the laminate.

II. Method for preparing polyester release film

According to another embodiment of the present disclosure, there is provided a method for preparing a polyester release film, the method comprising the steps of: (i) preparing a polyester base layer stretched in the machine direction (MD); ( ii) A release layer is formed by coating at least one surface of the polyester base layer with an aqueous coating composition comprising an adhesive containing a polyester resin and a polyolefin wax; and (iii) heat treating a laminate comprising a polyester base layer and a release layer formed on the polyester base layer while stretching the laminate in the transverse direction (TD) , wherein step (iii) is performed while passing the laminate through a heat treatment device in which the total heat of air supplied to the passing zone is 222,000 kcal/min to 229,000 kcal/min.

(i) Carrying out the step of preparing a polyester base layer stretched in the machine direction (MD).

The polyester base layer is made of polyester resin. As the polyester base layer, a known polyester base layer in the field to which the present invention pertains can be used without particular limitation.

Preparation of polyester by stretching in the machine direction (MD, or machine direction) base layer. Preferably, the polyester base layer can be stretched from 2 times to 5 times in the machine direction (MD).

The polyester base layer preferably has a thickness of 10 microns to 300 microns.

Subsequently, (ii) performing a step of forming a release layer by coating at least one surface of the polyester base layer with an aqueous coating composition comprising a polyester resin-containing binder and Polyolefin wax dispersed on adhesive.

The aqueous coating composition is used to form a release layer on the polyester base layer.

The aqueous coating composition includes a binder and a polyolefin wax dispersed on the binder.

The adhesive contains polyester resin. The adhesive may further contain acrylic resin.

Specific details of the polyester resin, acrylic resin, and polyolefin wax are the same as those described in <I. Polyester Release Mold>.

For example, in terms of solid content, the adhesive may preferably contain polyester resin and acrylic resin in a weight ratio of 1:0.5 to 1:1.5.

In addition, the aqueous coating composition preferably contains 10 to 40 parts by weight of the polyolefin wax based on 100 parts by weight of the binder.

The total amount of binder and polyolefin wax included in the aqueous coating composition may be 4.5 to 6.4 wt %, 4.5 to 6.0 wt %, 4.5 to 5.8 wt %, 5.0 wt % based on solids content % to 5.8% by weight or 5.1% to 5.8% by weight.

If the total amount of the binder and the polyolefin wax contained in the aqueous coating composition is too low in solid content, transfer characteristics and releasability may deteriorate, and triboelectricity may increase. In addition, if the total amount in the solid content is too high, the process coatability may be deteriorated, for example, fine pores may appear during the preparation of the polyester release film.

In the aqueous coating composition, if necessary, further additives such as polysiloxane-based wetting agents, fluorine-based wetting agents, curing agents, acid catalysts, slip agents, defoamers, wetting agents, interface Active agents, thickeners, plasticizers, antioxidants, UV absorbers, preservatives and crosslinkers. Additives can be selectively used within limits that do not impair the physical properties of the aqueous coating composition and release layer.

The aqueous coating composition can be prepared by uniformly mixing the components described above and water. The solids content of the aqueous coating composition may be 20% to 60% by weight for the efficiency of the coating process.

The release layer may be formed on at least one surface of the polyester base layer by a tandem coating method using an aqueous coating composition. Since the release layer is formed by the tandem coating method, it has excellent adhesion to the polyester base layer, and can exhibit excellent moisture resistance and solvent resistance, while having a thin coating thickness.

The tandem coating method can be performed using known equipment.

When performing tandem coating, the aqueous coating composition may be coated to a thickness of 20 nm to 200 nm after final stretching and drying of the release layer.

The release layer is formed by coating an aqueous coating composition on the polyester base layer, and then removing moisture from the aqueous coating composition, followed by curing.

Subsequently, (iii) a step of performing heat treatment on the laminate while stretching the laminate in a transverse direction (TD, or width direction), the laminate comprising a polyester base layer and formed on the polyester base layer release layer on top.

The laminate can be stretched 2x to 5x in the transverse direction (TD).

For example, a release layer is formed on a polyester base layer uniaxially stretched in the machine direction (MD), and then the release layer is stretched in the transverse direction (TD). Through this stretching process, the polyester base layer is biaxially stretched in the machine direction and the transverse direction, and is separated from the The mold layer is uniaxially stretched in the transverse direction.

Step (iii) may be performed using a conventional heat treatment device such as a tenter. In step (iii), the plies are continuously passed through a tenter frame.

The plies are preheated as they pass through the front zone of the tenter, stretched in the transverse direction (TD) as they pass through the middle zone of the tenter, and preheated as they pass through the rear zone of the tenter. Heat treatment means heating while maintaining the tensile force applied to the laminate during stretching in the transverse direction.

Preferably, step (iii) can be performed while passing the laminate through a thermal treatment device in which the total amount of heat supplied to the air passing through the area is 222,000 kcal/min to 229,000 kcal/min. The laminate passing through the heat treatment apparatus is subjected to transverse stretching and heat treatment while being exposed to the above-mentioned total heat.

For example, step (iii) may be performed while passing the laminate through a thermal treatment device in which the total heat of the air supplied to the overall passage area is 222,000 kcal/min or greater, 225,000 kcal/min or more than 225,000 kcal/min, or 226,000 kcal/min or more than 226,000 kcal/min and 229,000 kcal/min or less than 229,000 kcal/min, 228,000 kcal/min or less than 228,000 kcal/min minutes, or 227,000 kcal/min or less than 227,000 kcal/min.

Specifically, step (iii) may be performed while passing the laminate through a heat treatment device in which the total heat of the air supplied to the overall passing area is 222,000 kcal/min to 229,000 kcal/min, 225,000 kcal/min cal/min to 229,000 kcal/min, 226,000 kcal/min to 229,000 kcal/min, 226,000 kcal/min to 228,000 kcal/min or 226,000 kcal/min to 227,000 kcal/min.

The amount of air supplied to the pass through the laminate in step (iii) can be calculated from information such as the temperature of the zone (°C), the mass of air supplied to the heat treatment device (kg/min), and the specific heat of the air (kcal/kg°C). The total heat (kcal) of the air in the whole area. The mass of air (kg/min) can be obtained from the volumetric flow rate of the air (standard cubic meters per minute) and the density of the air (kg/standard cubic meters).

For example, when the density of the air supplied to any area in the heat treatment device is 1.286 kg/standard cubic meter, the specific heat of the air is 0.24 kcal/kg °C, and the volume flow rate of the air is 380 standard cubic meters/ minute, the initial temperature of the air is 20°C, and the set temperature of the zone is 220°C, and the total heat (kcal) of the air supplied to the zone can be obtained by the following equations 1 and 2 as 23,456.64 kcal/min.

[Formula 1] Mass of air (kg/min) = volume flow rate of air (standard cubic meter/min) × density of air (kg/standard cubic meter)

[Formula 2] Heat of air (kcal/min) = Mass of air (kg/min) x specific heat of air (kcal/kg °C) x temperature change (°C)

And, when the channel length of the zone is 3 meters and the laminate passes through the zone at 100 m/min, the heat exposed by the laminate in the zone can be calculated as 7037 kcal/zone by the following Equation 3.

[Formula 3] Heat exposure of the laminate (kcal/area) = heat of air (kcal/min) × channel length of the area (m/area) × speed of the laminate (m/min)

According to an embodiment of the present disclosure, a method may be performed by a process comprising preheating the laminate by passing the laminate through an area supplied with 44,000 kcal/min to 46,000 kcal/min of heat; in a lateral direction (TD) a process of up-stretching a preheated laminate while passing it through a zone supplied with heat from 62,000 kcal/min to 64,000 kcal/min; and heat-treating the stretched laminate while passing it through a zone supplied with heat Process in the region of heat from 114,000 kcal/min to 120,000 kcal/min.

Preferably, a preheating process can be performed while passing the laminate through an area where 45,000 kcal/min to 46,000 kcal/min of heat is supplied.

Preferably, the stretching process in the transverse direction can be performed while passing the preheated laminate through a zone in which 63,000 kcal/min to 64,000 kcal/min of heat is supplied.

And, preferably, a heat treatment process can be performed while passing the stretched laminate through a supply of 115,000 kcal/min to 120,000 kcal/min, 115,000 kcal/min to 119,000 kcal/min, 116,000 kcal/min Min to 119,000 kcal/min, 117,000 kcal/min to 118,500 kcal/min or 118,000 kcal/min to 118,500 kcal/min calorie zone.

In step (iii), if necessary, the preheating process, the stretching process in the transverse direction and the heat treatment process may be performed in two or more zones in which the supplied heat is described above changes within the range.

As a non-limiting example, in step (iii), stretching and heat treatment in the transverse direction may be performed while passing the plies sequentially through two preheating zones, three stretching zones, and five heat treating zones.

If the total amount of heat supplied in step (iii) to the passing zone (in particular, the heat treatment zone after stretching in the transverse direction) is too low, the peelability of the polyester release film Separation and transfer characteristics can be poor, and triboelectricity can be increased. Also, if the total amount of heat supplied to the passing area (specifically, the heat treatment area after stretching in the transverse direction) in step (iii) is too high, the surface energy of the polyester release film decreases, thereby reducing processing Coatability.

In addition, in step (iii), the laminate is compared at a speed of 80m/min to 120m/min, 90m/min to 110m/min, or 90m/min to 100m/min Preferably through a heat treatment device.

In performing step (iii), the plies are preferably passed through the heat treatment apparatus at the above rate ranges so that the plies are exposed to an appropriate amount of heat in each region and to adequately perform the stretching and heat treatment in the transverse direction.

Step (iii) may be performed at 120°C to 245°C.

For example, step (iii) may be performed by the following process: preheating the laminate at 120°C to 150°C; stretching the preheated laminate in the transverse direction at 130°C to 150°C; and at 215 The stretched laminate is heat treated at 245°C to 245°C.

In particular, at 215°C or greater, 220°C or greater, 225°C or greater than 225°C or 230°C or greater than 230°C and 245°C or less than 245°C, 240°C or less than 240°C or 235°C Or the heat treatment process of the stretched laminate is performed at less than 235°C. Specifically, the stretching of the stretched laminate may be performed at 215°C to 245°C, 220°C to 245°C, 220°C to 240°C, 225°C to 240°C, 225°C to 235°C, or 230°C to 235°C heat treatment process.

If the temperature of the heat treatment process of the stretched laminate is too low, the peelability of the polyester release film may be poor, and the triboelectricity may be increased. In addition, if the temperature of the heat treatment process is too high, processing coatability may be deteriorated, and fine pores may appear, for example, during the preparation of polyester release films.

After performing step (iii), a process of relaxing by 2% to 10% in the machine direction and the transverse direction, respectively, may be performed at 150°C to 200°C.

The final thickness of the polyester release film obtained through the above process may be 20 to 100 microns, 30 to 80 microns, or 30 to 50 microns.

[Beneficial effect]

According to the present disclosure, there is provided a polyester release film made of non-polysiloxane material and having excellent peelability and low triboelectricity, and a preparation method thereof. A polyester release film can be suitably used as a release base film in the production of thin polarizing plates.

[Detailed description of this embodiment]

In the following, preferred examples are presented to aid the understanding of the present invention. However, the following examples are only for illustrating the present invention and do not limit the present invention.

Preparation Example 1

50 mol % of a diol component containing diethylene glycol and ethylene glycol in a molar ratio of 5:5 and 50 mol % of a diol component containing terephthalic acid in a molar ratio of 8.5: 1.5 and The acid component of sulfoterephthalic acid was used to obtain the first polyester resin (weight average molecular weight: 10,000 g/mol).

100 parts by weight of the first polyester resin and 25 parts by weight of polyethylene wax were added to distilled water, and stirred for 30 minutes to prepare a first resin composition (solid content: 20% by weight).

Preparation Example 2

50 mol % of a diol component containing diethylene glycol and ethylene glycol in a molar ratio of 5:5 and 50 mol % of a diol component containing terephthalic acid in a molar ratio of 8.5: 1.5 and The acid component of sulfoterephthalic acid was used to obtain a second polyester resin (weight average molecular weight: 3000 g/mol).

60 mol % of glycidyl acrylate and 40 mol % of vinyl propionate were copolymerized to obtain an acrylic resin (weight average molecular weight: 50,000 g/mol).

50 parts by weight of the second polyester resin, 50 parts by weight of the acrylic resin, and 25 parts by weight of the polyethylene wax were added to distilled water and stirred for 30 minutes to prepare a second resin composition (solid content: 20% by weight).

Example 1

(i) Preparation of a polyethylene terephthalate (PET) base layer stretched 3.5 times in the machine direction (MD). Specifically, the PET wafer from which the moisture was removed to 100 ppm or less was injected into a melt extruder and melted, and then rapidly with a casting drum having a surface temperature of 20° C. while being extruded through the T-die Cool and solidify to prepare PET flakes. The prepared PET sheet was stretched 3.5 times in the machine direction at 110° C., and then cooled to room temperature to obtain a PET base layer.

(ii) mixing 14.3% by weight (solid content: 20% by weight) of the first resin composition according to Preparation Example 1, 14.3% by weight (solid content: 20% by weight) of the second resin composition according to Preparation Example 2, 0.2 wt% of a polysiloxane based humectant (manufactured by Dow Corning, Q2-5212, solids content: 90 wt%), 0.2 wt% of a fluorine-based humectant (manufactured by DuPont, FS-31 , solid content: 25% by weight) and 71% by weight of distilled water to prepare an aqueous coating composition.

The aqueous coating composition was applied to a thickness of 70 nm on the PET base layer after final drying using a gravure coater to form a laminate.

(iii) Subsequently, a step of heat-treating the laminate while stretching it 4 times in the transverse direction (TD) in a tenter divided into a preheating zone, a stretching zone, and a heat-treating zone is performed.

Step (iii) was performed, while the laminate (initial width: 5.12 meters, initial thickness: 152 microns) was sequentially passed through a total length of 33 meters at a moving speed of 100 meters per minute including the preheating zone, stretching zone and the tenter frame in the heat treatment zone.

Step (iii) was performed while passing the plies through a tenter frame with a total heat supply to the air passing through the zone of 226,400 kcal/min.

In step (iii), the density of the air supplied to the tenter is 1.286 kg/standard cubic meter, the specific heat of the air is confirmed to be 0.24 kcal/kg °C, and the volumetric flow rate of the air is 270 standard cubic meters/ Adjustable from minutes to 680 standard cubic meters per minute.

Specifically, the laminate passed through a preheating zone (channel length: 7.5 meters) in which a heat of 45,000 kcal/min was supplied at a temperature of about 120°C to 130°C. Subsequently, the preheated laminate was stretched 4 times in the transverse direction while passing through a stretching zone in which a heat of 63,200 kcal/min was supplied at a temperature of about 130°C to 140°C (channel length: 10.5 meters) . Subsequently, the stretched laminate was heat treated while the laminate passed through a heat treatment zone (channel length: 15 meters) in which 118,200 kcal/min of heat was supplied at a temperature of 230°C to 235°C.

After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Example 2

A PET base layer stretched 3.5 times in the machine direction (MD) was prepared in the same manner as in Example 1 .

25.75 wt % of the first resin composition (solid content: 20 wt %) according to Preparation Example 1, 0.81 wt % of a melamine curing agent (manufactured by DIC) were mixed manufactured, J-101LF, solid content: 70 wt %), 0.48 wt % acid catalyst (manufactured by KING INDUSTRY, Nacure 8924, solid content: 25 wt %), 0.2 wt % polysilicon An oxygen-based wetting agent (manufactured by Dow Corning, Q2-5212, solid content: 90% by weight) and 72.8% by weight of distilled water were used to prepare an aqueous coating composition.

The aqueous coating composition was applied to a thickness of 70 nm on the PET base layer after final drying using a gravure coater to form a laminate. Next, stretching in the transverse direction (TD) and heat treatment were performed in the same manner as in Example 1. After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Comparative Example 1

A PET base layer stretched 3.5 times in the machine direction (MD) was prepared in the same manner as in Example 1 .

10.75 wt % (solid content: 20 wt %) of the first resin composition according to Preparation Example 1, 10.75 wt % (solid content: 20 wt %) of the second resin composition according to Preparation Example 2, 0.2 wt % of polysiloxane-based wetting agent (manufactured by Dow Corning, Q2-5212, solid content: 90% by weight), 0.2% by weight fluorine-based wetting agent (manufactured by DuPont, FS-31, solid content: 25% by weight) and 78.1 % by weight of distilled water to prepare an aqueous coating composition.

The aqueous coating composition was applied to a thickness of 70 nm on the PET base layer after final drying using a gravure coater to form a laminate. Next, stretching in the transverse direction (TD) and heat treatment were performed in the same manner as in Example 1. After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Comparative Example 2

A PET base layer stretched 3.5 times in the machine direction (MD) was prepared in the same manner as in Example 1 .

17.9 wt % (solid content: 20 wt %) of the first resin composition according to Preparation Example 1, 17.9 wt % (solid content: 20 wt %) of the second resin composition according to Preparation Example 2, 0.2 wt % were mixed of polysiloxane-based wetting agent (manufactured by Dow Corning, Q2-5212, solid content: 90% by weight), 0.2% by weight fluorine-based wetting agent (manufactured by DuPont, FS-31, solid content: 25% by weight) and 63.8 % by weight of distilled water to prepare an aqueous coating composition.

The aqueous coating composition was applied to a thickness of 70 nm on the PET base layer after final drying using a gravure coater to form a laminate. Next, stretching in the transverse direction (TD) and heat treatment were performed in the same manner as in Example 1. After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Comparative Example 3

A PET base layer stretched 3.5 times in the machine direction (MD) was prepared in the same manner as in Example 1 .

19.3 wt % of the first resin composition (solid content: 20 wt %) according to Preparation Example 1, 0.61 wt % of a melamine curing agent (manufactured by DIC, J-101LF, solid content: 70 wt %), 0.36 wt % were mixed % of acid catalyst (manufactured by King's Industries, USA, Nacure 8924, solid content: 25 wt %), 0.2 wt % of polysiloxane-based wetting agent (manufactured by Dow Corning, solid content: 90 wt %) and 79.5 wt % of distilled water to prepare an aqueous coating composition.

Aqueous coating was applied on the PET base layer after final drying using a gravure coater The coating composition was applied to a thickness of 70 nm to form a laminate. Next, stretching in the transverse direction (TD) and heat treatment were performed in the same manner as in Example 1. After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Comparative Example 4

A PET base layer stretched 3.5 times in the machine direction (MD) was prepared in the same manner as in Example 1 .

32.2 wt % of the first resin composition (solid content: 20 wt %) according to Preparation Example 1, 1.03 wt % of a melamine curing agent (manufactured by DIC, J-101LF, solid content: 70 wt %), 0.56 wt % were mixed % of acid catalyst (by King Industries, Inc., Nacure 8924, solids content: 25% by weight), 0.2% by weight of polysiloxane wetting agent (manufactured by Dow Corning, Q2-5212, solids content: 90% by weight) and 66% by weight of distilled water to prepare an aqueous coating composition.

The aqueous coating composition was applied to a thickness of 70 nm on the PET base layer after final drying using a gravure coater to form a laminate. Next, stretching in the transverse direction (TD) and heat treatment were performed in the same manner as in Example 1. After the heat treatment step, polyester release films with a total thickness of 38 microns were prepared for heat setting by relaxing 10% in the machine and transverse directions, respectively, at 200°C.

Comparative Example 5

A polyester release film having a thickness of 38 microns was prepared in the same manner as in Example 1, except that the total heat supplied to the passing area of the tenter frame in step (iii) was 221,400 kcal/min.

Specifically, the laminate passed through a preheating zone (channel length: 7.5 meters) in which a heat of 45,000 kcal/min was supplied at a temperature of about 120°C to 130°C. follow After that, the preheated laminate was stretched 4 times in the transverse direction while passing through a stretching zone in which 63,200 kcal/min of heat was supplied at a temperature of about 130°C to 140°C (channel length: 10.5 meters) . Subsequently, the stretched laminate was heat-treated while passing through a heat-treatment zone (channel length: 15 meters) in which heat of 113,200 kcal/min was supplied at a temperature of 230°C to 235°C.

Comparative Example 6

A polyester release film having a thickness of 38 microns was prepared in the same manner as in Example 1, except that the total heat supplied to the passing area of the tenter frame in step (iii) was 229,200 kcal/min.

Specifically, the laminate passed through a preheating zone (channel length: 7.5 meters) in which a heat of 45,000 kcal/min was supplied at a temperature of about 120°C to 130°C. Subsequently, the preheated laminate was stretched 4 times in the transverse direction while passing through a stretching zone in which a heat of 63,200 kcal/min was supplied at a temperature of about 130°C to 140°C (channel length: 10.5 meters) . Subsequently, the stretched laminate was heat-treated while passing through a heat-treatment zone (channel length: 15 meters) in which heat of 121,000 kcal/min was supplied at a temperature of 230°C to 235°C.

Comparative Example 7

A polyester release film having a thickness of 38 microns was prepared in the same manner as in Example 2, except that the total heat supplied to the passing area of the tenter frame in step (iii) was 221,400 kcal/min.

Specifically, the laminate passed through a preheating zone (channel length: 7.5 meters) in which a heat of 45,000 kcal/min was supplied at a temperature of about 120°C to 130°C. Subsequently, the preheated laminate is stretched 4 times in the transverse direction while passing through a stretching zone in which 63,200 kcal/min of heat is supplied at a temperature of about 130°C to 140°C (pass Road length: 10.5 meters). Subsequently, the stretched laminate was heat-treated while passing through a heat-treatment zone (channel length: 15 meters) in which heat of 113,200 kcal/min was supplied at a temperature of 230°C to 235°C.

Comparative Example 8

A polyester release film having a thickness of 38 microns was prepared in the same manner as in Example 2, except that the total heat supplied to the passing area of the tenter frame in step (iii) was 229,200 kcal/min.

Specifically, the laminate passed through a preheating zone (channel length: 7.5 meters) in which a heat of 45,000 kcal/min was supplied at a temperature of about 120°C to 130°C. Subsequently, the preheated laminate was stretched 4 times in the transverse direction while passing through a stretching zone in which a heat of 63,200 kcal/min was supplied at a temperature of about 130°C to 140°C (channel length: 10.5 meters) . Subsequently, the stretched laminate was heat-treated while passing through a heat-treatment zone (channel length: 15 meters) in which heat of 121,000 kcal/min was supplied at a temperature of 230°C to 235°C.

test case

(1) Optical properties

A haze meter (Nippon Denshoku, NDH 5000) was used to measure the haze and total light transmittance (TT) of the films of Examples and Comparative Examples.

(2) Transfer characteristics (transfer test)

After laminating the untreated PET base film on the release layer of the polyester release film, a load of 19.69 gf/cm (i.e. 50 gf/inch) was applied and left to stand at 45°C in an oven 24 hours. If the deviation of the water contact angle is Δ2° or more, it is indicated as having transfer (or O), and if there is no deviation in the water contact angle, it is indicated as to have no transition (or X).

(3) Water contact angle

A contact angle measuring device (KRÜSS, DSA 100) was used to measure the water contact angle with respect to the release layer of the membrane. 3 microliters of pure water (S1, volume mode) was dropped on the film sample, and the average water contact angle for 15 seconds was measured. A total of 5 measurements were taken, and the average value thereof is listed below.

(4) Diiodomethane contact angle

The diiodomethane contact angle with respect to the release layer of the film was measured using a contact angle measuring device (Clues, DSA 100). 3 microliters of diiodomethane (S1, volume mode) was dropped on the film sample and the average diiodomethane contact angle was measured for 15 seconds. A total of 5 measurements were taken, and the average value thereof is listed below.

(5) Surface energy

The measurement results of the water contact angle and the diiodomethane contact angle were calculated using the Owens-Wendt method to calculate the surface energy of the release layer of the film.

(6) Process coatability

UV cured samples were prepared by coating a UV resin (Miwon Specialty Chemical Co., MIRAMER M1130) to a thickness of 10 microns on the release layer of the film. The samples were evaluated for process coatability according to the following criteria.

^* Class 1 - No small holes per unit area (square meters)

^* Category 2 - 2 small holes or less per unit area (square meters)

^* Class 3 - 5 small holes or less per unit area (square meters)

^* Class 4 - 10 small holes or less per unit area (square meters)

^* Level 5 - more than 10 small holes per unit area (square meters)

(7) Peel strength

The measurement of peel strength according to the standard test method of ASTM D903 involved the following steps: A first sample was prepared by coating the release layer of the film with UV resin (Meiyuan Specialty Chemicals, M1130) as a 10 micron thickness to form a UV cured layer; a second was prepared by rubbing the TESA tape back and forth twice over the cured UV resin layer of the first sample using a 2 liter rubber roller, and then cutting it to a size of 2.5 mm x 15 cm sample; and a load of 70 g/cm² was applied to the second sample and allowed to stand at room temperature for 30 minutes, followed by a peel tester (manufactured by Chem Instrument, AR-1000) at 300 mm/min Peel rate 180 degrees peel off TESA tape.

(8) Triboelectric

The triboelectricity of the polyester release film was measured using a rotating electrostatic tester (Daei Kagaku Seiki MFG, RST-300a). The A side (the side of the release layer in the polyester release film) was attached to the rotating drum, and the B side (the side of the polyester base layer sample on which the release layer was not formed) was fixed to the rubbing table. While the A side was rotated at a rotational speed of 300 rpm under mechanical control, the B side was rubbed against the friction table for 180 seconds, and then the amount of charge was measured.

S ^* : The total amount (in solid content) of the binder and polyolefin wax contained in the aqueous coating composition

T ^* : Heat treatment temperature in tenter (°C)

H ^* : total heat in the tenter frame (kcal)

A ^* : Turbidity (%)

B ^* : Total light transmittance (%)

C ^* : Water contact angle (°)

D ^* : Diiodomethane contact angle (°)

E ^* : Surface energy (mN/m)

F*: Process coatability (grade)

G ^* : Peel Strength (gram force/inch or grams force/cm)

H ^* : transfer characteristic

I ^* : Triboelectricity (Volt)

Referring to Tables 1 and 2, it was confirmed that the polyester release films of the Examples had excellent releasability and lower triboelectricity, as well as excellent transfer characteristics and process coatability, compared to the release films of the Comparative Examples sex.

Claims (19)

A polyester release film, comprising a polyester base layer and a release layer, the release layer is formed on at least one surface of the polyester base layer, wherein the release layer comprises a polyester resin-containing An adhesive and a polyolefin wax dispersed on the adhesive having a peel strength of 3.94 g/cm or less and a triboelectricity of less than 500 volts, wherein the adhesive contained in the adhesive The weight average molecular weight of the polyester resin is 2000 g/mol to 25,000 g/mol. The polyester release film according to claim 1, wherein the adhesive further contains acrylic resin. The polyester release film according to claim 2, wherein in terms of solid content, the adhesive contains the polyester resin and the acrylic resin in a weight ratio of 1:0.5 to 1:1.5. The polyester release film according to claim 2, wherein the weight average molecular weight of the acrylic resin contained in the adhesive is 20,000 g/mol to 70,000 g/mol. The polyester release film according to claim 1, wherein the release layer contains 10 to 40 parts by weight of the polyolefin wax based on 100 parts by weight of the adhesive. The polyester release film according to claim 1, wherein the polyolefin wax is at least one wax selected from the group consisting of polyethylene wax and polypropylene wax. The polyester release film according to claim 1, wherein the polyester release film has a haze of 3.90% or less, and the process coatability satisfies the following Equation 1: [Equation 1]N _H = 0 In Equation 1, _NH is per unit area (square) when UV resin is applied to a thickness of 10 microns on the release layer of the polyester release film and the UV resin is cured meters) the number of small holes produced. The polyester release film according to claim 1, wherein the polyester base layer has a thickness of 10 micrometers to 300 micrometers, and the release layer has a thickness of 20 nanometers to 200 nanometers. The polyester release film of claim 1, wherein the polyester base layer is biaxially stretched in the machine direction (MD) and the transverse direction (TD), and the release layer is stretched in the transverse direction (TD) ) uniaxially stretched. A polyester release film for a thin polarizing plate, comprising a polyester base layer having a thickness of 10 to 300 microns and a thickness of 20 to 20 nanometers formed by serial coating on the polyester base layer. A 200-nm release layer, wherein the release layer comprises an adhesive containing a polyester resin and a polyolefin wax dispersed on the adhesive, and has a 3.94 gf/cm or less of 3.94 gf/cm Peel strength and triboelectricity less than 500 volts, wherein the weight average molecular weight of the polyester resin contained in the adhesive is 2000 g/mol to 25,000 g/mol. A method for preparing the polyester release film as claimed in claim 1, It includes the following steps: (i) preparing a polyester base layer stretched in the machine direction (MD); (ii) by applying an aqueous coating composition to at least one of the polyester base layers. a surface to form a release layer, the aqueous coating composition includes an adhesive containing a polyester resin and a polyolefin wax dispersed on the adhesive; and (iii) a heat-treated laminate, the laminate comprising the the polyester base layer and the release layer formed on the polyester base layer, while stretching the laminate in the transverse direction (TD), wherein the step (iii) is performed simultaneously The laminate was passed through a thermal treatment apparatus in which the total heat of air supplied to the passing area was 222,000 kcal/min to 229,000 kcal/min. The method for preparing the polyester release film according to claim 11, wherein the aqueous coating composition further comprises an acrylic resin as the adhesive. The method for preparing the polyester release film of claim 1 according to claim 12, wherein in terms of solid content, the adhesive contains the polymer in a weight ratio of 1:0.5 to 1:1.5 Ester resin and the acrylic resin. The method for preparing the polyester release film according to claim 11, wherein based on 100 parts by weight of the adhesive, the aqueous coating composition comprises 10 parts by weight to 40 parts by weight parts by weight of the polyolefin wax. Use as claimed in claim 11 for the preparation of polyesters as claimed in claim 1 The method for a release film, wherein the total amount of the binder and the polyolefin wax contained in the aqueous coating composition is 4.5 wt % to 6.4 wt % in terms of solid content. The method for preparing the polyester release film according to claim 1 , wherein the polyester base layer is coated by a tandem coating method using the aqueous coating composition. The release layer is formed on at least one surface. The method for producing the polyester release film as claimed in claim 1 1 , wherein the stretching in the machine direction (MD) is performed by stretching 2 times to 5 times, respectively Extends to the stretching in the transverse direction (TD). The method for preparing the polyester release film as claimed in claim 1 1 , wherein the laminate is in the step (iii) at 80 m/min to 120 m/min through the heat treatment device. The method for preparing the polyester release film according to claim 1 1 , wherein the step (iii) comprises: by passing the laminate through a supply of 44,000 kcal/min to 46,000 kcal/min area of heat to preheat the laminate process; stretching the preheated laminate in the transverse direction (TD) while feeding 62,000 kcal/min through it process to a zone of heat of 64,000 kcal/min; and heat-treating the stretched laminate while supplying 114,000 kcal through it cal/min to 120,000 kcal/min thermal zone process.